Involute checking fixture and tailstock mounting therefor



Sept. 22, 1953 J. 11.. JESSUP ET AL 2,652,665

7 INVOLUTE CHECKING FIXTURE AND TAILSTOCK MOUNTING THEREFOR Filed Aug. 22, 1947 4 Sheets-Sheet 1 Sept. 22, 1953 J. L. JESSUP ETAL 2,652,665

INVOLUTE CHECKING FIXTURE AND TAILSTOCK MOUNTING THEREFOR Filed Aug. 22, 1947 4 Sheets-Sheet 2 INVENTORLS'. 7; vies A rfzsa 21 Herry /7( dafer g.

Sept. 22, 1953 J. JESSUP EI'AL 2,652,665

INVOLUTE CHECKING FIXTURE AND TAILSTOCK MOUNTING THEREFOR Filed Aug. 22, 1947 4 Sheets-Sheet 3 INVENTORS. E' rfamea l r/ssvp Her-2y H Gafey.

7 BY M,

, /7 TOR/VE/Sf Sept. 22, 1953 J. JESSUP ETAL 2,652,665

INVOLUTE CHECKING FIXTURE AND TAILSTOCK MOUNTING THEREFOR Filed Aug. 22, 1947 4 Sheets-Sheet 4 22 57 w Pa E INVENTORS J5me: A Jssvf Harv ff Gofber y Patenteci Sept. 22, 1953 7 226524565 Aiwiiflri STOCK MOUNTINGTHEREFOR' tends through the side wall 2| of the base I3, the opening 39 in the slide 31, and is threadably received at 64 in the opposite side wall 29, of the base I3. By tightening the cap screw 63, the side walls 20 and 2| are compressed against the side faces of the slide 31, and prevent movement of the slide with respect to the base after it has been longitudinally adjusted. Depending dust plates 65 are secured to opposite ends of the slide 31, to prevent the ingress of dirt between the slide and the plate 23.

Forwardly of the opening 39, the slide 31 is formed with a slot or cutout portion 61, in which is received members to be hereinafter described. The extreme forward end of the slide 31 is provided with a keyway II in which is received a complemental key portion of a center I3. The center I3 is rigidly connected to the forward end of the slide 31 by means of countersunk cap screws I5. The pointed end of the center is adapted to engage one end of a broach 11, as illustrated in Fig. l, and the opposite end of the broach I1 is conventionally supported in the grinding machine index head (not shown).

It will thus be seen'that the center 73 may be adjusted vertically to align with the center of the index head by loosening the cap screw 63 and the nut 51 on the stem of block 5|, and then threading the nuts 29 upwardly or downwardly. Horizontal adjustment is accomplished by turning handle 49, so that the center I3 will properly engage the end of the broach TI to support the same while involute teeth or splines 719 are ground thereon by means of a form grinding wheel 88, illustrated in dot and dash lines in Fig. 1.

The fixture for checking the form and spacing of the broach teeth I9 is generally indicated at 3|, and is illustrated in the drawings in its position on the tailstock. However, it is to be understood that during the machining operation, the checking fixture BI is detached from the tailstock, and only after the grinding operation has been completed, is it secured to the tailstock in order to accurately check the form and spacing of the broach teeth. This arrangement, therefore permits the broach teeth to be checked, without removing the broach from the grinding machine. 7

\ The checking fixture 8| includes a'stationary, generally T-shaped plate 83. The horizontal leg 85, of the, plate 33, is provided with a longitudinal slot ill in the underside thereof, as shown in Fig. 6, in which a key 39 is secured by means of countersunk screws 9|. The key 89 is adapted to be received in a slot 93 formed in the upper surface of the slide 37, above the opening 39 therein. Screws 95 are provided for rigidly securing the plate 83 to the slide 37, as can be seen in Fig. 2. The vertical leg 91 of the plate 83 extends above and below the horizontal leg 85 and when the parts are assembled, the rear face of the lower portion of the vertical leg 9? abuts against the back face of the slot or cutout portion 61 of the slide 31, so that the plate 83 is rigidly held with respect to the slide.

A second vertical plate 99 is pivotally mounted on the plate 83 by means of a pivot pin, generally indicated at WI, and the rear. face'of the plate 99 engages and slides on the front face of the vertical leg 91 of the plate .33. The

pivot pin IIJI is formed with an annular hub-.

like portion I93, intermediate its ends, which is received in a recess I95 in the lower portion of second plate 99. A threaded stem I01 extends rearwardly from the pivot pin hub portion I03, through an aligned threaded aperture I99 in the lower portion of the plate 83 and carries a nut HI which secures the pivot pin IIII fixedly with respect to the plate 83 and preloads bearings Ill as hereinafter explained. Forwardly of the pivot pin hublike portion I93, a circumferential flange I13 is formed, which has outwardly converging conical side walls, and which is located within a recess II5 of the second plate 99. A plurality of steel balls II'I are disposed around the outer periphery of the recess H5 and on opposite sides of the pivot pin flange II3. A centrally apertured cover plate H9 is secured in the front face of the plate 99, by means of countersunk screws I2I and thrusts against the steel balls Ill. By tightening the nut III on the threaded stem of the pivot pin, the flange H3 is pulled rearwardly against the rear set of steel balls 1 il so as to force the second plate 99 against the plate 93, and thereby prevent any play between the plates 83 and 99 respectively, but still permit the second plate 99 to be swung in a true vertical plane, with respect to the first plate 83. The plate II9 loads the two sets of balls against the conical flange II3 and the recess II5, thus providing a preloaded ball bearing pivot for the,

plate 99.

A tapered pin I23 is adapted to be inserted through an aperture I25, adjacent the upper end of the plate 83, into a tapered aperture I21 of the swinging plate 99, to center the swinging plate with respect to the stationary plate 93, for a reason which will hereinafter appear.

In order to hold the second plate 99 against movement with respect to the first plate, when the tapered pin I23 is removed, a clamp I3I.is provided adjacent the upper end of the plate 83. The clamp i3| has a rearwardly extending threaded stem $33 which projects through an aperture I35, adjacent the upper end of the first plate 83. The clamp I3I is of a generally hollow rectangular shape, as seen in Fig. 2, and the front wall thereof has a downwardly projecting nose I3! formed thereon. The clamp nose I31 fits over, and engages the front faoeof an upstanding arcuate flange I39 formed on the upper arcu-a ate surface of the plate 99. A thumb nut I43 is threaded onto the outer end of the threaded stem I33, of the clamp, so that by adjusting the thumb nut the clamp may be tightened, to hold the plate 99 against movement with respect to the first plate 83, or loosened, to allow the second plate to swing relative to the first plate.

Due to the hollow construction of the clamp I3I the top surface of the flange I39, of the swinging plate 99, and the forward portion of the upper arcuate surface of the plate 83 may be viewed by looking down through the center of the clamp. Secured to the upper surface of the flange I39 is a plate 595 having a protractor scale marked thereon. A similar plate M6, having a Vernier scale marked thereon, is secured to the upper surface of the plate 83, so that when the second plate is centered with respect to the plate 83, the zero marking on the Vernier scale will be aligned with the zero marking on the regular scale. Therefore when plate 99 is swung relative to plate 83 the amount of such movement may be read by means of this protractor and Vernier scale.

The opposite side walls. of the swinging plate 99 are cut back so as to converge rearwardly and provide ineffect a male dovetail I99 (Fig. 2). A

.harlike member I5:I is mounted for verticalimove- .ment on the .front .face of the swinging plate 99 and-held in sliding engagement therewith by meanscf ra demaledovetail formed on the rear iace thereof, which receives the male .dovetail I49 of theswinging {plate .99. The female .dove- \tailof the bar .I5.I formed by meansof arearwardly projecting leg L53, on one end of the bar I 5I and an adjustable fgib -I.55 on the opposite -.end. Thesgib 4.55 may be loosened or tightened against the male dovetail 449 to =eliminatetplay ,yet permit vertical-sliding of the bar I 5I on the swinging -.plate 99.

As best shown in Figures .3 and 8 the lower portion of the rear face of the bar [:51 is -provided with .awpairof spaced recesses I 91 in :each of which, is received a roller 459. Each of the rollers I 59 is journaledon a shaft 15.3 Joy means .of bearings 15!. The free ends of the .shafts :t63 are fixed in apertures L95 in thebar E51, so that the rollers I59 are rotatably jjournaled on the-bar I 51.

An annular base circle roller I9 is ,journaled .on the forward shank portion H38 of the pivot .pin 1.9], and is adapted to be locked thereto by means of a set screw I199. Thelouterperi-phery'of the roller I fi-I, belowand on opposite sides of the pivot pin shank IE8 is cut to provide notches .I-'I-I. As can be seen .in Fig. 8, a hook like :mem- 'ber H3 is received in each of the notches I II --and has one end :of a flat Efiexible steel tangent .band. I'I-.5 secured thereto. .Each of the bands extends around a portion of the outer periphrery' of the roller IE], on opposite sides thereof and in axially spaced relation to each other so .as to cross and extend outwardly inopposite directions FalQng a common tangentjto the roller. The opposite ends of the bands are connected .to the ends of a: tangent :bar I19 which has a dflat surface 1159 that, in operation, rests -.on the .bands at the point of their common tangency to the base circle roller 69. The-iconnection between the ends of the bands and- -the=ends of the tangent bar is effected :by means of screws :2 LI. :Eaohv of the screws IZI I- is received in a :notch in the underside of depending.fiangesM-Z, at each end of the tangentbar. The-:outer :face .of eachfiangeZZIZ isrecessed to receive'lthe-inner end of a thumb :nut 2L3, which inturn thread ably receives the outer endof one of the screws -2I-I, so. that by tightening the thumb nut 2.13, each .band I75 will be tightened against the base .roll. tIi-l.

The tangent bar- I19 has its back face abutting against the lower portion'of the front .face .ofswinging plate 99,. and the cover plate H9.

'.- I.ntermediate the front and. rear faces of the tangent bar I39 an upwardly opening, longitudilnally' extending, T-slot I-9I is provided; in which is-received the head of a headed. bolt 183-. y The threaded-stem of the bolt I99. isfixedin the underside of. the. bar I5I- near its'center, sons to slidably and loosely secure the tangentbar II9 -.to-.the bar- I5.I:. The topface ofgthe rear. portion of-the tangent bar :IIIS is pitched downward an:- gularly at. I85, as seen-in Fig. '3, -andtherollers .15 9-which are supported by the bar -I 5tareadapted. to roll on this pitched surface. In order :to .preventyertical play between the base roller 1:621 .and zthe. .ta ngentgbar Il9', -the.lower end of :a ithumb screw L89, which-is threadedinto acforwardly projecting boss- 'I99.--.on thenpper end of t-he swingingplate-:9B isadaptedto be screwed downwardly against the -top. f;ace of the bar, 15: [and -thus;:load.-ther-rollers- ;I59;:.against the surface "respective end of the tangent bar.

1:85 of the tangent bar I19. Thisiorcesthe bottom face of the tangent bar against the tangent .bands I15, and the roller I61, and-the inclined face-4'85 prevents the tangent bar from 'moving away from the front face of swinging plate 99. -In this way, therefore, the 'bar I51 and its transversely spaced rollers I59 efiectively hold the tangent. bar I19 against the base roll IIi Iand therefore eliminate any play which may occur .therebetween. n I

.In order etO prevent the tangent :bar from-slid ing transversely out of the bar I-5I' when the bands -II5 are removed, .a stud I92 and a pin I92 are provided in the opposite ends of the T-slot 19! of the tangent bar, to act as stops .for the headed bolt 4.83. .In order to positively hold the tangent bar in its central position during adjustment, a tapered pin I93 is adapted to .be slidably received in,a forwardly projecting. boss .I94 of the :bar .I5I, in a notch 1.95, .in the topface of the tangent .bar, and adjacent the .-front face thereof. I

The forward face of the tangent-bar .I1I:9\i'- s .fcrmed withaidovetail recess I96 which receives a dovetail projection .I'9'I formedon the baclaface of a plate I99, which is therefore movable .transversely with respect to the tangentbar I19} End plates. -29I aresecured by means-of screws 292, to each end. of the-sliding plate .I99and the-end plates overlap a portion ofiithe tangent barend faces. Theend faces oflthe tangent bar 1119 are notched inwardly to permit the overlapping portion of the end plates 20.I to be receivedtherein when the plate I99 is moved. relative to the tangent bar. A thumb screw .293 is .threadably received in each oi the endplates .Z'Iil .and-theinner end of each thumb screw is adapted to abut against the inner end of the notch .cut.-i n i.ts By turning the thumb screws 203, the sliding.- .plate .I-99-can be moved transversely with respect to the tangent bar .and fixed relative thereto inany .desired position.

As canbe seen in Figs. 1 and 4- the bottom edge of the plate I99 is notched at 294,-. adjacent-one end thereof.- The front face of the tangent-bar I-.'I-9, behind the notchtfifi is tapped and counter- .sunk to receive a cap screw 295;- The-tangent .bar is slottedealong the line'295: (Fig-.1), inter-- .mediate its ends in .the-vicinity-of the screw 295 .so that when the screw is threaded into-1115s aperture and tightened, the dovetailwportion ofthe tangent bar will collapse againstthe dovetail portion of the -sliding plate 1:99 and clamp the plate I99 against movement relative to the tangent bar.

, An upstanding gauge lug. 291 is'formedcnthe top-face of the-sliding plate I99, adjacent-one endthereofias can be seen in Fig.4. A'djustably secured to the tangent 'bar I-I-9is an-upstanding gauge lug 299, which is spaced-longitudinally of the tangent bar from the Jug-2.91 and .isin align- ;ment therewith, so that the distance between the gauge lugs can bewaccurately measured by .gaugeblocks or-either. inside or outside calipers .-for reasons which will-hereinafter appear.

. Anindicator arm -2:I 9- :is: pivotally mountedbn the front-face-of the sliding plate I99, byimean's ofa. pin 229 which pivotallyconnectsz'a-pair vo'f transversely spaced upstanding-ears 221; formed on the rear, upper endcof saidiarm twthe oppozsite ends of a boss 2-23 formed: on the topc'fa'c'e of the plate F99. The" lower re'ar ken-d5 of the .arm 21.9 which .isin -the=.form:;of:;a' flatwplate is :Jadaptedwto-Ibe secured-to theefrontface" ofthe plate I99 by means of a thumb screw221. By unscrewing the thumb screw 221, the arm '2I9 may be swung upwardly with respect to the plate The'extreme forward end of the arm 2I9 has a vertically depending end 229 formed thereon, in which is received a screw 23I, having a conically pointed end 235. The pointed end 235 of the screw 23! rotatably supports the forward end of a pointer arm 239 through a bearing 249. The rear end of the pointer arm 239 has a similar bearing 24I mounted therein which receives the pointed end of a screw 243, which in turn is threaded into the rear end of the indicator arm 2I9.

A pointer 245 is mounted in the forward end of the pointer arm 239, by means of a threaded stem 241 and a nut 248, so that it is possible to adjust the pointer 245 vertically with respect to its arm 239. The end of the pointer 245, is adapted to contact the teeth or splines of the broach 11. In order to insure that any errors in the tooth form will be measured on a tangent to the base circle extending through the point of contact between the pointer 245 and the involute form, the end of the pointer is formed as a truncated cone which contacts the involute form at the edge of the base of the cone, as best shown in Figure 9. The diameter of the base of the cone is so correlated with the length of the pointer that on limited pivotal movements of the pointer, the point of contact between the pointer and the involute form travels in a straight line parallel with the tangent bar. A conventional dial indicator 249 is rigidly mounted on one of the ears 22I, of the indicator arm, adjacent the pair of cup shaped members 259 are threaded into the threaded cylindrical bore 258 of the housing 251, and thus form a cylindrical recess 269 having end walls 26I and 262, each of which has a central aperture 263 therethrough. Extending upwardly through the apertures 263 in the members 259 with substantial radial clearance, and through the recess 260 is a plunger 265 which has its upper end threaded, to receive thumb nuts 261 thereon. The hub portion 269 of the lower thumb nut 261 extends through the aperture 263 in the end wall 26I of the upper member 259. The lower end of the pin 265 is enlarged at 21I, to provide a shoulder. Disposed within the recess 260, and surrounding the pin '265, is a coil spring 213 which abuts loose washers 215 and 211 disposed above and below the spring, respectively. The washers 215 and 211 each have a pair of buttons 21B mounted on their outer faces at diametrically opposed points adjacent the outer edges of the washer, and a pair of diametrically opposed buttons 218 located adjacent the inner edges of the washer. The thumb nuts 261 are adjusted on the plunger 265 so that the buttons 219 on the upper washer 215 abut the lower end ofthe thumb nut hub portion 299, While its buttons 218 abut the end wall 261. The buttons 219 on the lower washer 211 then abut the upper end of the plunger shoulder portion 21I, and its buttons 218 abut the lower end wall 262. Under these circumstances the spring 213 is under compression. Thus the plunger 265 may be moved upwardly or downwardly against the action of the spring, but when the plunger is released, the spring and washers will return the plunger to its central position, as illustrated in Fig. 7 and positively hold it in that position.

The lower end of the plunger 265 is fixedly connected to the outer end of an arm portion 219, which extends outwardly on the opposite side of the pointer arm 239, from the arm portion 253 which contacts the dial indicator plunger. Therefore, the centering spring arrangement will positively zero the dial indicator, and will always return the pointer 245 and the needle of the dial indicator to zero, after the same have been actuated, in either direction. If desired, the location of the pointer may be adjusted, by adjusting the cap members 259, within the housing 251, and then adjusting the thumb nuts 261, so that the spring and Washers will be in a centered position, as previously described.

In operation the center 13 of the tailstock H is engaged in the end of the broach 11, by adjusting its height, by means of the screws 25, as reviously described, and by adjusting it horizontally by means of the handle 49 and screw 41. After the broach has been ground by the grinding wheel 89, and it is desired to check the form and spacing of the involute teeth formed thereon, the grinding wheel is either removed or moved away from the tailstock. The checking fixture 8I, during the grinding operation is disassembled from the tailstock.

While the checking fixture 8| is disassembled from the tailstock, the swinging plate 99 is centered on the stationary plate by means of the tapered pin I23. The gib I55 is then adjusted to take up any play between the roller bar I5I and the swinging plate 99. The tangent bar and indicator assembly is removed from the fixture by removing the stud I92 from one end of the tangent bar and sliding the same outwardly from the roller bar I5I so that the headed bolt I83 is removed from the T-slot I8I. The tangent bar is then set on end on a flat surface such as a surface plate and the point of the pointer 2451s adjusted to the exact known distance from the notch I in the tangent bar. This distance may be, for example, one inch and the adjustment can be made by turning the thumb screws 203 so as to move the sliding plate I99 and the pointer 245 the necessary amount. Also by adjusting the cap members 259 in the centering spring housing, as previously described, the pointer may be moved a limited distance, with respect to the tangent bar without introducing errors due to the angular movement of the pointer. The sliding plate I99 is then secured against movement to the tangent bar I19 by means of the cap screw 295, and the gauge lug 209, on the tangent bar, is adjusted to exactly one inch, or the known distance, from the gauge lug 261 on the plate I99.

The proper size base roll I61 is then placed on the forward end of the pivot pin IUI, so that the diameter of the base roll plus twice the thickness of the bands (which are formed of shim stock) corresponds exactly to the diameter of the base circle on which the involute teeth of the broach are generated. The tangent bar I19 is then replaced in the fixture and the stud I92 threaded into the tangent bar to prevent it from sliding off the roller bar. The tapered pin I93 1s then inserted into the notch I95 in the tangent bar to positively secure the tangent bar in its 9. central position. The swinging plate 99' is brought to its central position and" the taper pin I23 inserted. The bands I15 are then connected to the base roll rer; while the latter is free to rotate on the forward end of the pivot pin. The tangent bands are then tightened by adjusting the thumb nuts 2P3. Since at this time the roll [-61 is free to rotate, equaltension in the two bands is assured. The 'set screw "59' is then tightened to secure the base roll It! against rotation, on the forward portion of the pivot pin HI I-. The thumb screw I89 is threaded downwardly in the boss I90, of plate 99', against the bar l5-l toload its rollers I59 againstthetangent bar, to thereby take up any play between the tangent bar and the base roll lei, so' that the tangent bar can roll on the base roll I 61 but cannot slide with respect thereto. All of these adjustments insure that the center of the pointer will lie exactly in the vertical plane containing theaxis of the breach when the fixture is assembled and the outer faces of the gaugelugs 2-9-1 and 209 are exactly one inch apart. Once these adjustments are made they need not be repeated when the unit isremoved from or installed on the tailstock, or when base rolls are changed.

The checking fixture is then mounted on the tailstock by securing the stationary plate 83 on the upper surface of the tail'stock by means of key 89 and screws: 95 as previously described-L Itwill be understood thatthebro'a-ch maybe rotated and fixed by meansof the usual index head in the position which the twouppermost teeth in the transverse plane: ofpoihter 245 are at equal distances on. opposite sides of the vertical center line. Accordingly the pointer will now be disposed exactly midway between the two uppermost involute teeth H3 on the broach TI.

By calculation, the tangential distance from the vertical center line of the base circle of the teeth on the broach re to the point on the involute curve at which the involute tooth form begins can be determined; The pointer 2J5 can then be moved tangentially" a calculated distance by adjusting thethumb screws 2-93; and measur ing'the calculated amount of movementbetween the gauge lugs 201 and 289. The'amount of movement provided should; of course, be less than the calculated distance by the radius of the conical base of the pointer 2452 The contacting edge of the pointer 245 will now lie at the base of the tooth form to be checked. By then removing the tapered pin I23 and. the tapered pin l 93', which fits'i'nto'the notchof the tangent'bar; the plate 99 can be swung'about'thepivot pinlll'l so. as to cause the tangent bar I79 to roll on the base roll [61. This will cause the pointer 2'45 tomove on the path of the desired tooth form; and-the dial indicator 249 will indicate any variations in the form of the tooth being checked; The amount which the plate 99 has moved angu larly can be determinedby reading the scales mounted on the upper end of the swinging plate 519 and stationary plate 83., and, thus the location ofany. errors in form determined;

In most involutex gear and spline teeth'th'e' base circle is of smaller diameter than the root diameter, of the teeth andconsequentlythe pointer 2.4.5 cannot engage the. involute: form at the base circle. It is for this reason that the indicator arm is pivoted'at 22.0 so that it can be swung upwardly out of; the way until after the pivoted plate has been swung. as above described, far enough to permit engagement'of the point'cnwith any variations in the form of the tooth being checked as well as its distance from the other tooth will be indicated on the dial indicator. It will be noted that in this case the opposite side of the pointer" is engaging the tooth and that therefore the indicator is actuated in the opposite direction if" the tooth spacing is too small. In order to insure accurate readings in opposite directions from aneutral point the indicating mechanism includes the previously described positive centering device within housing 251. This permits measurements of tooth spacing which has hitherto been impossible with involute checking devices.

It will therefore be seen that both the form and the spacing of the teeth of the breach, splined shaft or gear can be quickly and accurately checked, without removing the workpiecefrom the grinding machine. The entire checking fixturn can be removed from the tailst'ock asa unit and reinstalled without di'fficulty andwithout. disturbing any of the adjustments. This greatly facilitates checking of involute forms.

While the use of tension band's connecting the tangent bar and base roll is preferred it. will" be apparent that the bands maybe omitted, if: desired, and friction between the tangent bar and base roll relied upon to prevent slippage. In. that case the base roll will be the full" base circle diameter of the form checked. When the bands are used the effective diameter of. the base roller is its actual diameter plus twice. the thickness of the bands.

I claim:

1. A fixture for checking the form and spacing of circu-mferentially spaced involute teeth of a member, including: a. rollerelement having an outside diameter equal tothat of. the base circle on which theinvolute teeth of the member are generated, means for supporting said. roller element in axial alignment with said toothed member, a tangent'barsupported on said roller element and adaptedsto be rolled thereon, a. pointer, means pivotally mounting: said pointer-on said tangent bar; indicator means operatively connected to said pointer, adjustablecentering means supported on said tangent bar and; operatively connected tov said pointer for opera-timely returning said indicator and said pointer to: zero following displacement in either of twoopposite directions, means for adjusting: said pointer to a known point with respectltdsaid involute teeth base circle, and means for shifting: said: pointer a known distance parallel to a tangent to said base circle.

2. A fixture for checking the form and spacing of circumferentiall'y spaced involute: teeth. of a workpiece, including aroller element having an outsidediameter equal to that of the base circle on which the involute teeth of the-workpiece are generated; means for supporting said roller". element in axial alignment with said workpiece, a tangent bar supported on said roller elementand adapted tobe swung in rolling'engagement'thereiwith, a member mounted on one face of said tangent bar and movable longitudinally with respect thereto, a pair of members mounted respectively on said tangent bar and member and having surfaces which extend transversely to the tangent bar and are longitudinally aligned so that they may cooperate with a measuring device for measuring the longitudinal position of said member with respect to said tangent bar, means for fixing the tangent bar in a position of reference, a work engaging element movably mounted on said member and having a work engaging portion movable approximately parallel to the tangent bar, said portion of the element being located in a known position with respect to the theoretical location of the involute form to be checked when said tangent bar is in said position of reference and said surfaces on said members are spaced a predetermined distance, an indicator mechanism operatively connected to said element, and means for adjusting said longitudinally movable member parallel to said tangent bar, whereby the work engaging surface on said element can be located at the theoretical position of the tooth form to be checked by changing the distance between the surfaces on said members by a calculated amount.

3. A fixture for checking the form and spacing of circumferentially spaced involute teeth of a workpiece including a roller element having an outside diameter equal to that of the base circle on which the involute teeth of the workpiece are generated; means for supporting said roller element in axial alignment with said workpiece, a tangent bar supported on said roller element and adapted to be swung in rolling engagement therewith, a member mounted on one face of said tangent bar and movable longitudinally with respect thereto, a pair of members mounted respectively on said tangent bar and member and having surfaces which extend transversely to the tangent bar and are longitudinally aligned so that they may cooperate with a measuring device for measuring the longitudinal position of said member with respect to said tangent bar, means for fixing the tangent bar in a position of reference, a work engaging element movably mounted on said member and having a work engaging portion movable approximately parallel to the tangent bar, said portion of the element being located in a known position with respect to the theoretical location of the involute form to be checked when said tangent bar is in said position of reference and said surfaces on said members are spaced a predetermined distance, an indicator mechanism operatively connected to said element, means for adjusting said longitudinally movable member parallel to said tangent bar, whereby the work engaging surface on said element can be located at the theoretical position of the tooth form to be checked by changing the distance between the surfaces on said members by a calculated amount, and centering means operatively connected to said work engaging element for operatively returning said indicator to zero following displacement in either of two opposite directions.

4. A fixture for checking the form and spacing of circumferentially spaced involute teeth of a workpiece, including a detachable roller element having an outside diameter equal to that of the base circle on which the involute teeth of the workpiece are generated, means for supporting said element in axial alignment with said workpiece, a tangent bar supported on said roller element and adapted to be swung in rolling engagement therewith, a member mounted on one face of said tangent bar and movable longitudinally with respect thereto, a pair of members mounted respectively on said tangent bar and member and having surfaces which extend transversely to the tangent bar and are longitudinally aligned so that they may cooperate with a measuring device for measuring the longitudinal position of said member with respect to said tangent bar, detachable tension bands for connecting said roller element and said tangent bar to prevent slippage therebetween, means for fixing said tangent bar in a position of reference during the tensioning of said bands, a work engaging element movably mounted on said member and having a work engaging portion movable approximately parallel to the tangent bar, said portion of the element being located in a known position with respect to the theoretical location of the involute form to be checked when said tangent bar is in said position of reference and said surfaces on said members are spaced a predetermined distance, an indicator mechanism operatively connected to said element, and means for adjusting said longitudinally movable member parallel to said tangent bar, whereby the work engaging surface on said element can be located at the theoretical position of the tooth form to be checked by changing the distance between the surfaces on said members by a calculated amount.

5. A fixture for checking the form and spacing of circumferentially spaced involute teeth of a workpiece including a spindle having its axis fixed on the axis of said workpiece, a detachable roller element mounted on said spindle and having an outside diameter equal to that of the base circle on which the involute teeth of the workpiece are generated, a tangent bar supported on said roller element and adapted to be swung in rolling engagement therewith, a member mounted on one face of said tangent bar and movable longitudinally with respect thereto, a pair of members mounted respectively on said tangent bar and member and having surfaces which extend transversely to the tangent bar and are longitudinally aligned so that they may cooperate with a measuring device for measuring the longitudinal position of said member with respect to said tangent bar, detachable tension bands for connecting said roller element and said tangent bar to prevent slippage therebetween, releasable means for locking said roller element to said spindle so that said roller element is freely rotatable on said spindle during the tensioning of said bands, means for fixing said tangent bar in a position of reference during the tensioning of said bands, a work engaging element movably mounted on said member and having a work engaging portion movable approximately parallel to the tangent bar, said portion of the element being located in a known position with respect to the theoretical location of the involute form to be checked when said tangent bar is in said position of reference and said surfaces on said members are spaced a predetermined distance, an indicator mechanism operatively connected to said element, and means for adjusting said longitudinally movable member parallel to said tangent bar, whereby the work engaging surface on said element can be located at the theoretical position of the tooth form to be checked by changing the distance between the surfaces on said members by a calculated amount.

6. In combination, a tailstock for a grinding machine, a center rigidly secured to said tailstock, said tailstock having a fiat surface fixed relative to said center, a detachable involute tooth checking fixture mounted on said tailstock fiat surface, said fixture including a member having a flat surface engaging said tailstock flat surface, a roller element having an outside diameter equal to that of the base circle on which the involute teeth of the member are registered, means connected with said fixture for supporting said roller element in axial alignment with said center, a tangent bar supported and adapted to roll on said roller element, a pointer, and means mounting said pointer on said tangent bar.

JAMES L. JESSUP.

HARRY H. GOTBERG.

Name Date Olson 2 May 27, 1919 Number Number 14 Name Date Simmons Jan. 12, 1932 Crocker June 7, 1932 Swain Oct. 25, 1932 Olson Jan. 7, 1936 stowcll Apr. 7, 1936 Miller Nov. 10, 1936 Pelphrey July 2'7, 1937 Osplack Dec. 30, 1941 Asbridge May 5, 1942 Kullman Aug. 10, 1943 Lersch Apr. 2, 1946 Dyson May 13, 1947 

